1. Field of the Invention
The present invention relates to a method of manufacturing a multilayer printed circuit board, and more particularly to a method of manufacturing a multilayer printed circuit board with a built-in electronic device.
2. Description of the Related Art
At present, speed and density are two major requirements of the development of high technologies, and it is a primary objective to satisfy consumer requirements as well as lowering the production cost. Thus, electronic and mobile communication products tend to be developed with a light, thin, short and compact design and come with multi-functions, high reliability and low price. These products are generally developed in generations of every three to five years. To comply with this trend, passive components occupying the largest area in a circuit design of electronic products are integrated.
As to a printed circuit board, the area occupied by the electronic devices has been the greatest limitation for miniaturizing the products. With too many soldering points on the printed circuit board, the reliability will be lowered, and the manufacturing cost will be increased. For a better function, a smaller volume and a lighter weight, related manufacturers and designers try to create more spaces and enhance the functions of modules within the area of the baseboard of the printed circuit board. Obviously, integration and embedment are important factors for the development trend of passive electronic devices.
To overcome the aforementioned issues, R.O.C. Pat. No. 518616 disclosed a method of manufacturing a multilayer printed circuit board with embedded passive components, and this method integrates several film electronic devices into a multilayer printed circuit board, and the key measure of the method is the manufacturing capability of embedding thick and thin film electronic devices into the printed circuit board, such that after the electronic device is integrated into the multilayer printed circuit board while maintaining a good electric precision and minimizing the difference between the original design values, the overall manufacturing process will be more complicated.
The foregoing drawbacks are common, and thus manufacturers try to overcome the drawbacks by the following. R.O.C. Pat. No. I246383 disclosed another method of manufacturing a multilayer printed circuit board of embedded passive components, and this method comprises the steps of: providing a conductive foil having at least one pair of metal bumps, and coupling a passive component to the corresponding metal bump; laminating an organic insulating layer onto a core board; laminating the conductive foil onto the organic insulating layer; and forming a circuit pattern on the conductive foil and coupling with the passive component. However, when the conductive foil coupled with the passive component is laminated onto the organic insulating layer, the passive component has a specific height, and there is a risk of damaging the components or affecting the product reliability, since the organic insulating layer will press the components directly during a thermal pressing process.